Extreme pressure lubricant compositions



Patented June 18, 1957 EXTREME PRESSURE LUBRICANT COIVIPOSITION Harold J. Watson and Herman I). Kluge, Fislikill, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application November 30, 1953, Serial No. 395,269

Claims. (Cl. 252-475) This invention relates to lubricating compositions characterized by anticorrosive properties. More particularly, the invention discloses a novel lubricant additive which is effective in preventing the corrosion of silver bearings.

In a commonly-owned copending application, Serial No" 392,502, filed November 16, 1953, in the names of Herman D. Kluge and Thomas C. Roddy, Jr., it is disclosed that rhodanine and its S-hydrocarbon-substituted derivatives impart excellent extreme pressure and anticorrosive properties to lubricating compositions. In this copending application, it is prescribed that the groups essential to the function of rhodanine and its derivatives as extreme pressure, anticorrosive and antioxidant agents are =C=S, =NH and =C=O groups of the rhodanine nucleus; rhodanine and its 5-hydrocarbon-substituted compounds are disclosed as imparting the desirable combination of extreme pressure, anticorrosive and antioxidant properties to lubricant compositions. The subject invention is directed to the discovery that 3-hydrocarbon-substituted rhodanines, also identified as 3-hydrocarbon-substituted 2-thiono4-ketothiazolidines, when incorporated in lubricant compositions, inhibit silver corrosion.

The novel lubricating compositions of this invention comprise an oleaginous material having lubricating properties as the major component and a minor amount sufficient to impart anticorrosive properties thereto of a 3-hydrocarbon-substituted rhodanine compound of the general formula wherein R is a monovalent hydrocarbon radical residue.

Monovalent hydrocarbon residue comprises aliphatic formula:

Rhodanine compounds containing a hydrocarbon residue substituted on the 3 position and used in the lubricating compositions of this invention are exemplified by the following: 3-ethylrhodanine, 3-n-butylrhodanine, 3-methylrhodanine, 3-t-amylrhodanine, 3-n-octylrhodanine, 3-ndodecylrhodanine, 3-1'-butenylrhodanine, 3-phenylrhodanine, 3-o-tolylrhodanine, 3-benzylrhodanine, 3-cyclohexylrhodanine and 3-2'-ethylcyclohexylrhodanine.

Apparently, the presence of the =NH group in the rhodanine radical is necessary for the effectiveness of rhodanine compounds as extreme pressure and anti-wear agents. However, the anticorrosive properties of the rhodanine radical do not appear to be dependent upon the presence of a =NH group in the rhodanine radical, as is evidenced by the fact that the 3-hydrocarbon-substituted rhodanine compounds are effective in inhibiting silver corrosion when incorporated in lubricant compositions.

The presence of silver bearings in diesel engines and in aircraft engines has necessitated that lubricants for these uses be inhibited against silver corrosion. The 3-hydrocarbon-substituted rhodanine compounds of this invention are effective in combating corrosion of silver bearings and bushings even when used in very small concentrations of the order of 0.01 to 2.0 percent.

The incorporation of 3-hydrocarbon-substituted rhodanine compounds imparts exceptional antioxidant and anticorrosive properties to both greases and lube oil compositions. The concentration of the additive in both greases and oils is usually within the 0.01 to 2.0 weight percent concentration range; in general, concentrations of rhodanine compounds in the upper portion of the cited range are used in grease compositions, whereas concentrations in the lower part of the prescribed limits are employed in lube oil compositions.

The oleaginous lubricating base can be a hydrocarbon mineral oil, a synthetic lubricating base or mixtures thereof. It a hydrocarbon mineral oil is the base, it is either a parafiin base or a naphthene base fraction which advantageously has undergone solvent refining to improve its lubricity and its viscosity-temperature relationships. For certain applications such as greases, straight vacuum distillate lube fractions that have not undergone extensive solvent refining are employed as the lubricating base in which 3-hydrocarbon-substituted rhodanine compounds are incorporated. In general, it can be stated that a wide variety of lube oil fractions are contemplated for use in the lubricating compositions of this invention; for example, paraffin base and naphthene base lube oil fractions having SUS viscosity at F. between 50 and 5,000 may be used as the base oil in the compositions of this invention.

The synthetic lubricating bases are usually of the ester or ether type. High molecular weight, high boiling liquid aliphatic dicarboxylic acid esters possess excellent viscosity-temperature relationships and lubricating properties and are finding ever increasing utilization in lube oils and greases adapted for high and low temperature lubrication;

, esters of this type are used in the formulation of jet engine oils and of greases designed for low temperature operation. Examples of this class of synthetic lubricating bases are the diesters of acids such as sebacic, adipic, azelaic, alkenyl-succinic, etc.; specific examples of these diesters are di-Z-ethylhexyl sebacate, di-2-ethylhexyl azelate, di-Z-ethylhexyl adipate, di-n-amyl sebacate, di-2- ethylhexyl-n-dodecyl succinate, di-Z-ethoxyethyl sebacate, di-2'-methoxy-2-ethoxyethyl sebacate (the methyl carbitol diester), di-2-ethyl-2-n-butoxyethyl sebacate. (the 2-ethlybutyl cellosolve diester), di-Z-n-butoxyethyl azelate (the n-butyl cellosolve diester), and di-2'-n-butoxy-2- ethoxyethyl-n-octyl succinate (the n-butyl carbitol diester).

Polyester lubricants formed by a reaction of an aliphatic dicarboxylic acid of the type previously described, a glycol and a monofunctional aliphatic monohydroxy alcohol or an aliphatic monocarboxylic acid in specified mol ratios are also employed as the synthetic lubricating base in the compositions of this invention; polyesters of this type are described in U. 5. 2,628,974. Polyesters formed by reaction of a mixture containing specified amounts of dipropylene glycol, sebacic acid and Z-ethylhexanol and of a mixture containing adipic acid, diethylene glycol and 2-ethylhexanoic acid illustrate this class of synthetic polyester lubricating bases.

Polyalkylene ethers as illustrated by polyglycols are also used as the lubricating base in the compositionsof this invention. Polyethylene glycol, polypropylene glycol, polybutylene glycols and mixed polyethylene-polypropylene glycols are examples of this class of synthetic lubricating bases.

The sulfur analogs of the above-described diesters, polyesters and polyalkylene ethers are also used in the formulation of the lubricating compositionsof this invention. Dithioesters are exemplified by di-2-ethylhexyl thiosebacate and di-n-octyl thioadipate; polyethylene thioglycol is an example of the sulfur analogs of the polyalkylene glycols; sulfur analogs of polyesters are exemplified by the reaction product of adipic acid, thioglycol and 2- ethylhexyl mercaptan.

The lubricant compositions containing 3-hydrocarbonsubstituted rhodanines have a wide variety of applications. Since these compounds impart antioxidant and anticorrosive properties to lubricant compositions even when present in very small concentrations, the lubricating compositions of this invention are designed for a wide variety of uses. A partial list of their uses is as follows: motor oils for lubrication of internal combustion autoengines, airplane oils, diesel oils, jet engine oils which are usually of the synthetic base variety, cutting oils, grinding oils, cylinder oils, hydraulic oils, automatic transmission fluids and valve oils. Greases containing 3-hydrocarbon-substituted rhodanines find application as chassis greases, ball and roller bearing greases, rail and flange lubricants, all types of gear lubricants, traction motor lubricants and all types of bearing lubricants.

3-hydrocarbon-substituted rhodanine' compounds are compatible with a wide variety of additives employed in the formulation of lube oils and greases. In most applications of the lubricants of this invention, other additives will be incorporated to help the lubricant meet the specifications prescribed for a specific utilization. Accordingly, in most lube oil compositions, 3-hydrocarbon-substituted rhodanine compounds are used in conjunction with one or more of the following types of additives: detergents, illustrated by salts of petroleum sulfonates and divalent alkaline earth metal salts of alkylphenols; antioxidants as illustrated by phenothiazine and polyalkyl-substituted phenols; corrosion inhibitors such as sulfurized terpenes; anti-rust agents as illustrated by alkenyl succinic acids; extreme pressure agents as illustrated by arylphosphates, sulfurized oils and fats, chlorinated hydrocarbons and sulfo-chlorinated hydrocarbons and organic acids. In greases, the most common additives, with which S-hydrocarbon-substituted rhodanine compounds are associated, Y

are antioxidant and extreme pressure agents; antioxidants are exemplified by phenyl alpha-naphthylamine; extreme pressure agents are similar to those employed in lube oils.

The effectiveness of 3-hydrocarbon substituted rhodanine compounds in combating silver corrosion was demonstrated in the EMD corrosion test which is used to determine the corrosiveness of heavy duty lubricating oils toward silver metal. The test gives an indication whether the oil is suitable for use in EMD (Electromotive Divi-. sion) diesel engines containing. silver-plated wrist pin bushings. V

The EMD corrosion test is run by placing silver strips or silver-plated wrist pin bushings in the sample of oil under test which is maintained with stirring at 300 R. P. M. at a temperature of 300 F.i2 F. The appearance and weight changes of the strips or bushings are determined periodically with 24 and 72 hours being the most common test periods employed. If the silverplated wrist pin bushing, which has an approximate size of 3" x l x 0.25" is used, it is pretreated at a temperature of about 140 F. with acetic acid-hydrogen peroxide solution comprising 3 parts glacial acetic acid and 1 part 30,.

4 5 percent hydrogen peroxide solution to remove lead flashing from the surface. After complete removal of the lead as determined by visual observation, the bushing is immersed in distilled water, dried, polished with steel wool, cleaned with lintless paper and weighed. In the following test, silver strips which have a surface area equivalent to that of exposed silver on the bushing, specifically, 3.50" x 0.75" x 0.005", were employed. With the silver strips, the acetic acid-hydrogen peroxide treatment is eliminated and the strip is directly polished with steel wool, cleaned-with lintless-paper and weighed to the nearest mg. a

In the test, all observations and weight changes are recorded; on the basis of the observation and weight changes, the oil is rated according to the following classifications: 7

Appearance and Wt. Change of Silver Specimen After Classification Appearance Unchanged:

Max. 5 mg. wt. change 6-25 mg. wt. change-- Over 25 mg. wt. change Discoloration or non-scaly, non-flaking deposit on strip:

Max. 5 mg. Wt. change 6-25 mg. wt. change Over 25 mg. wt. change- Scaly or flaking deposit on stri in the same oil is rated If strips from duplicate tests do not fall classification, the test is repeated and the as 2 of the 3 strips indicate.

The base oil used in the EMD corrosion test was a heavy duty lube oil containing a high concentration of detergent and inhibitor; the reference oil was an SAE 40 grade mixture having a V. I. of 55 and comprising 47.2 percent solvent refined paraflin residuum, 41.0 percent acid refined naphthene distillate fraction and 11.8 percent solvent refined paraffin distillate and containing 2.4'

percent basic barium sulfonate, 0.75 percent zinc alkyl dithiophosphate, 0.37 percent barium alkyl dithiophosphate and 0.225 percent neutral terpene-P255 reaction product. I are well known lubricant additives, which are more particularly described as follows: Basic barium sulfonate designates products resulting from the reaction of petroleum sulfonic acids with barium hydroxide in such proportions that the resulting mixture contains one free.

TABLE I EMD corrosion test (24 hr.)

Silver Wt. Silver Appear- Change, ance Rating Base 011 -14 Black flaky 5 deposit. Base oil+0.25% 3-(2-ethylhexyl) 0 Black powdery 2 rhodanine. deposit.

Obviously, many modifications and variations of the invention as above set forth may be made without departing fromthe spirit and scope thereof, and, therefore,

The additives used in the above composition only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A lubricating composition comprising a mineral lubricating oil as the major component and a minor amount suflicient to impart anticorrosive properties thereto of a 3-hydrocarbon-substituted rhodanine compound having the general formula O=CUNR O C=S H: 8

wherein R is a monovalent hydrocarbon residue.

2. A lubricating composition as described in claim 1 in which said rhodanine compound comprises 0.01 to 2.0 percent of the total composition.

References Cited in the file of this patent UNITED STATES PATENTS Loane Apr. 11, 1939 Lincoln et al Sept. 3, 1940 

1. A LUBRICATING COMPOSITION COMPRISING A MINERAL LUBRICATING OIL AS THE MAJOR COMPONENT AND A MINOR AMOUNT SUFFICIENT TO IMPART ANTICORROSIVE PROPERTIES THERETO OF A 3-HYDROCARBON-SUBSTITUTED RHODANINE COMPOUND HAVING THE GENERAL FORMULA 